This application claims the benefit of Korean patent application No. 2000-51747, filed Sep. 1, 2000 in Korea, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to an optical detecting sensor, and more particularly, to a thin film transistor (TFT) type optical detecting sensor using a small-sized drive integrated circuit (IC).
2. Discussion of the Related Art
Generally, optical detecting sensors are used in facsimile and digital copying machines, and in fingerprint recognition systems as an image reader. The optical detecting sensor stores electric charge in accordance with an intensity of light that is reflected from a detecting subject, and then outputs the electric charge via a drive circuit. In recent years, a TFT-type optical detecting sensor has been suggested in which the TFT changes its electrical characteristics in response to incident light.
The TFT-type optical sensor includes a light source that generates light, a window that introduces the light to a subject for detection, a sensor TFT, a storage capacitor, and a switch TFT. The sensor TFT generates an optical current in accordance with the intensity of the light reflected from the subject, and the storage capacitor receives the optical current and stores an electric charge indicative of the optical current. This electric charge represents reflected light intensity data. Then, the switch TFT transfers there reflected intensity light data from the storage capacitor to a main system in accordance with a control signal received from an exterior circuit.
FIG. 1 shows a conventional TFT-type optical sensor including an array substrate 1, and a backlight unit 2 disposed beneath the array substrate 1. The array substrate 1 detects the presence of a subject, stores data for related to the subject, and transmits the data to a main system (not shown), such as the fingerprint recognition system, for example. The backlight unit 2 provides light to the array substrate 1. At this point, the array substrate 1 includes a plurality of unit pixels xe2x80x9cPxe2x80x9d (in FIG. 2) each having a sensor TFT xe2x80x9cT1xe2x80x9d (in FIG. 2), a storage capacitor xe2x80x9cCxe2x80x9d (in FIG. 3), and a switch TFT xe2x80x9cT2xe2x80x9d (in FIG. 2).
FIGS. 2 and 3 show the unit pixel xe2x80x9cPxe2x80x9d of the array substrate 1 (in FIG. 1) of the conventional TFT-type optical sensor. As shown, a sensor gate line 21, a sensor data line 61, a switch gate line 25, and a switch data line 65 help to define the unit pixel xe2x80x9cP.xe2x80x9d The sensor gate line 21 and the sensor data line 61 are formed orthogonal to each other so as to cross each other, and the switch gate line 25 and the switch data line 65 are spaced apart from the sensor gate line 21 and the sensor data line 61, respectively.
The unit pixel xe2x80x9cPxe2x80x9d is divided into a photo-sensing region xe2x80x9cA,xe2x80x9d a storing region xe2x80x9cB,xe2x80x9d and a switching region xe2x80x9cC,xe2x80x9d all which are formed on a transparent substrate 10. A sensor gate electrode 22, a first storage electrode 24, and a switch gate electrode 26 are disposed in the photo-sensing region xe2x80x9cA,xe2x80x9d the storing region xe2x80x9cB,xe2x80x9d and the switching region xe2x80x9cC,xe2x80x9d respectively. The sensor gate electrode 22 and the switch gate electrode 26 integrally protrude from the sensor gate line 21 and the switch gate line 25, respectively. Alternatively, parts of the sensor gate line 21 and the switch gate line 25 may not protrude, but used as the sensor gate electrode 22 and the switch gate electrode 26, respectively. The first storage electrode 24 integrally protrudes from the sensor gate line 21.
In FIG. 3, a first insulating layer 30 covers the sensor electrode 22, the first storage electrode 24, and the switch gate electrode 26. On the first insulating layer 30, a sensor silicon layer 41 and a switch silicon layer 42 are formed in the sensing region xe2x80x9cAxe2x80x9d and the switching region xe2x80x9cB,xe2x80x9d respectively. A sensor ohmic contact layer 52 and a switch ohmic contact layer 54 are formed on portions of the sensor silicon layer 41 and the switch silicon layer 42, respectively. A sensor source electrode 62 and a sensor drain electrode 63 are formed over the sensor silicon layer 41, and a switch source electrode 66 and a switch drain electrode 67 are formed over the switch silicon layer 42. A first storage electrode 24 integrally protrudes from the sensor gate line 21 toward the unit pixel region xe2x80x9cP.xe2x80x9d The sensor source electrode 62 is connected with the sensor data line 61, and the sensor drain electrode 63 is spaced apart from the sensor source electrode 62 with the sensor gate electrode 22 centered therebetween. The switch source electrode 66 is connected with the switch data line 65, and the switch drain electrode 67 is spaced apart from the switch source electrode 65 with the switch gate electrode 26 centered therebetween. A second storage electrode 64 is formed connecting the switch drain electrode 67 and the sensor drain electrode 63, and the second storage electrode 64 overlaps the first storage electrode 24.
A second insulating layer 70 covers the sensor source electrode 62, the sensor drain electrode 63, the second storage electrode 64, the switch source electrode 66, and the switch drain electrode 67. A shielding pattern 80 that can be made of an opaque material is formed on the second insulating layer 70 over the switch silicon layer 42.
As shown in FIG. 4, the array substrate 1, having the unit pixels xe2x80x9cPxe2x80x9d as shown in FIG. 2, is connected with a plurality of output lines 92 that are electrically connected with a drive integrated circuit (IC) 93. Specifically, each switch data line 65 of FIG. 2 in the array substrate 1 is electrically connected with a corresponding output line 92. Therefore, when the switch TFT xe2x80x9cT2xe2x80x9d (in FIG. 2) switches data, the data is transferred to the drive IC 93 via the output line 92, such that the main system (not shown) can read the data from the drive IC 93.
When the backlight unit 2 of FIG. 1 is switched on to produce light, the sensor TFT xe2x80x9cT1xe2x80x9d of FIG. 2 generates data representative of reflected light, and the storage capacitor xe2x80x9cCxe2x80x9d of FIG. 3 stores the data. Then, the switch TFT xe2x80x9cT2xe2x80x9d of FIG. 2 switches the data in accordance with a control signal received from an exterior circuit (not shown). The switched data is subsequently transferred to the drive IC 93 via the switch data line 65 of FIG. 2 and the output line 92.
As previously mentioned, each of the plurality of data lines 65 of FIG. 2 are correspondingly connected with the same number of output lines 92. Moreover, the drive IC 93 may have a plurality of sub-circuits (not shown) each connecting with a corresponding output line 92. In other words, the drive IC 93 of the conventional TFT-type optical detecting sensor has the same number of sub-circuits as the plurality of output lines 92. Accordingly, the drive IC 93 may be very large in size and very complicated to manufacture, thereby creating high material cost and low manufacturing yield.
Accordingly, the present invention is directed to a TFT-type optical detecting sensor that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an improved TFT type optical sensor implementing a small-sized drive IC.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a thin film transistor (TFT) type optical detecting sensor includes an array substrate provided with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors, a backlight unit disposed beneath the array substrate to provide the light to the plurality of regions, and a drive IC including a plurality of sub-circuits, wherein an nth sub-circuit is connected with an nth output line of each region of the array substrate.
In another aspect, a thin film transistor-type optical detecting sensor includes an array substrate provided with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors to store charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors to selectively output the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors.
In another aspect, a method for manufacturing a thin film transistor optical detecting sensor includes the steps of providing an array substrate with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors, providing a backlight unit beneath the array substrate for providing the light for the plurality of regions, and providing a drive IC including a plurality of sub-circuits, wherein an nth sub-circuit is connected with an nth output line of each region of the array substrate.
In another aspect, a method of manufacturing an array substrate includes the steps of providing the array substrate with a plurality of regions, providing each of the plurality of regions with a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, providing each of the plurality of regions with a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, providing each of the plurality of regions with a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and providing each of the plurality of regions with a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.